That's according to a study presented in Madrid at the 12th congress of the European Federation of the Neurological Sciences.

The study included 236 adults with chronic low back pain who weren't depressed. They took Cymbalta or a placebo drug daily for 13 weeks.

Average weekly pain scores, measured before taking Cymbalta or the placebo and again at the end of the study, showed greater improvement in the Cymbalta group.

But that wasn't true in a second study, also presented in Madrid. In that study, there weren't any significant differences in before-and-after average weekly pain ratings among adults with chronic low back pain who took Cymbalta or a placebo once daily for 13 weeks. Cymbalta trumped the placebo from the third to the eleventh weeks, but not for the entire study overall.

Why did those results differ in the two studies? That's not clear. But the studies did differ slightly in their doses.

The study in which Cymbalta bested the placebo for average weekly pain scores used a 60 milligram dose of Cymbalta, a 120 milligram dose, or a placebo. The study in which Cymbalta didn't beat the placebo also included a lower (20 milligram) dose of Cymbalta, as well as the 60 milligram dose, 120 milligram dose, and placebo.

In both studies, side effects more commonly reported by patients taking Cymbalta included nausea, dry mouth, fatigue, diarrhea, excessive sweating (hyperhidrosis), dizziness, and constipation. That's in line with previous research on Cymbalta.

Both studies were funded by Eli Lilly and Company, the drug company that makes Cymbalta.